THE BULLETHOLES TEN

I do "The Bulletholes Ten". Its a ten minute walk around my apartment. If I'm feeling frisky, I'll do two laps.
I always think about my nephew Dave, and what it takes to do one of these ultras he runs. An Ultra is an 80 mile jog over mountains and rivers and stuff, and you have like 24 hours to do it. I wonder how long it will take me to achieve the mindset of the ultra runner.
I had told Dave about "The Bulletholes Ten" last month. I said "The great thing about "The Ten" is that if I decide I need to bail, I'm never more than 10 minutes from home".
Dave looked at me, pitifully.
"You mean five. You are never more than five minutes from home" he said.
I paused a moment, quickly reviewed my calculations, rocked back on my heels a bit and grinned.
"Right, Dave my boy! Only five minutes from home!"
Dave is not just a great Ultra runner. He's a damn fine mathematician as well.
He will be pleased to know I did two full "Tens" tonight.